Eco-Friendly Production of Boron Nitride Nanosheets via Deep Eutectic Solvents and Their Application in Enhancing Thermal Conductivity of PVDF Composites.

Boron nitride nanosheets (BNNS) are expected to be ideal fillers because of their high thermal conductivity and excellent electrical insulation. However, it is still an open challenge to produce BNNS on a large scale using ecofriendly solvents. Here, first, we demonstrate an effective liquid exfoliation method for producing BNNS via utilizing deep eutectic solvents (DES) composed of D,L-menthol and various acids with the assistance of ultrasonication. The results show that the BNNSs with sizes of 1-2 µm in width and 6-8 nm in thickness were successfully exfoliated with a DES formulation of D,L-menthol and decanoic acid. Second, the obtained BNNSs were used for fabricating 1,6-hexanediol diacrylate@polydopamine functionalized BNNS (HDDA@BNNSs-PDA) core-shell microspheres via a Pickering emulsion method. Furthermore, these microspheres were incorporated into a polyvinylidene fluoride (PVDF) matrix to construct 3D thermally conductive networks, leading to a substantial enhancement in the thermal conductivity of the resulting composites. Impressively, the composites with only 25 wt % of BNNS loading reach a high thermal conductivity of 3.20 W/m K, which is a 1500% increase over the pure polymer matrix. This work not only provides a significant way for producing BNNSs ecofriendly but also demonstrates a tactic for constructing 3D thermally conductive networks.

Mixotrophic denitrification processes based on composite filler for low carbon/nitrogen wastewater treatment.

Removal of nitrogen from wastewater with low carbon/nitrogen ratio was treated by using a denitrification packed bed reactor. Composite fillers with both autotrophic and heterotrophic denitrification capacity were prepared by mixing melted polycaprolactone and elemental sulfur at various alkalinity ratios (heterotrophic to autotrophic ratios of 1:2, 1:1, 3:2, and 2:1). Optimum denitrification was achieved at a ratio of 2:1. The diversity of the microbial community in the biofilm on the surface of the composite fillers showed that the increase of the elemental sulfur in the composite fillers has led to the increase of the microbial abundance. Furthermore, biofilm composition developed from a single dominant species to multiple species, and genes related to sulfur metabolism increased while those related to denitrification decreased slightly.

Effect of the gradual increase of Na2SO4 on performance and microbial diversity of aerobic granular sludge.

Aerobic granular sludge (AGS) is a promising technology in treating saline wastewater. The effects of sodium sulfate on contaminant removal performance and sludge characteristics of AGS were studied. The results showed that under the stress of sodium sulfate, AGS kept good removal performance of ammonia nitrogen (NH+ 4-N), chemical oxygen demand (COD), and total nitrogen (TN), with removal efficiency reaching 98.7%, 91.5% and 62.7%, respectively. When sodium sulfate reached 14700 mg/L, nitrite oxidizing bacteria (NOB) were inhibited and nitrite accumulation occurred, but it had little impact on total phosphorus (TP) removal. Under the stress of sodium sulfate, compactness and settling performance of AGS was enhanced. The microbial community greatly varied and the microbial diversity of aerobic granular sludge has decreased under the stress of sodium sulfate. The study reveals that AGS has great potential in application on treating saline wastewater.

Interfacial growth of metal-organic framework on carboxyl-functionalized carbon nanotubes for efficient dye adsorption and separation.

Hybrid nanocomposites based on UiO-66-NH2 and carboxyl-functionalized carbon nanotubes were developed in this study via different synthetic pathways. Combining them through interfacial in situ growth was beneficial for the better dispersity of UiO-66-NH2 in the CNTs@UiO-66-NH2 composite than physically mixing CNTs/UiO-66-NH2 and chemically bonded CNTs-CONH-UiO-66. Coordination between carboxyl groups of CNTs and zirconium ions resulted in the interfacial growth of UiO-66-NH2 on CNTs. Adsorption experiments showed that CNTs@UiO-66-NH2 exhibited the highest adsorption efficiency towards methyl orange (MO). The adsorption capacity of CNTs@UiO-66-NH2 was up to 392 mg g-1, which was 77.45% and 201.5% higher than those of CNTs-CONH-UiO-66 and CNTs/UiO-66-NH2 respectively. Moreover, CNTs@UiO-66-NH2 could selectively adsorb MO from the MO/MB mixture.